1. Mycorrhizal Fungi:
- Arbuscular Mycorrhizal Fungi (AMF):
a. AMF form associations with most flowering plants. They create external hyphae networks that significantly extend the root surface for nutrient absorption.
b. The fine fungal threads known as extraradical hyphae explore distant soil areas and gather nutrients unavailable to plant roots. These nutrients include phosphorus, zinc, copper, and other micronutrients.
c. In exchange, plants supply the mycorrhizal fungi with carbohydrates in the form of sugars, synthesized through photosynthesis.
2. Nitrogen-Fixing Bacteria:
- Rhizobia:
a. Nitrogen-fixing bacteria such as Rhizobia establish symbiotic relationships primarily with legumes (e.g., soybeans, peas, alfalfa).
b. The bacteria form root nodules, specialized structures housing them within the plant's roots.
c. Rhizobia possess the vital nitrogenase enzyme, which converts atmospheric nitrogen (N2) into ammonia (NH3).
d. The plant utilizes the synthesized ammonia for synthesizing essential nitrogen compounds such as amino acids, proteins, and nucleic acids.
e. In return, the plant provides Rhizobia with a protected environment, sugars, and other essential nutrients within the root nodules.
These microbial associations significantly improve the acquisition and utilization of nutrients by plants. By working together with bacteria and fungi, plants increase their tolerance to environmental stresses and thrive in various growing conditions.
